When to measure the Creatinine (Creat)/Albumin ratio and at what time?

From the Guidelines

The Creatinine/Albumin ratio, also known as the Albumin-to-Creatinine Ratio (ACR), should be measured in a random urine sample, preferably in the first void of the morning 1. It is recommended to perform this test in patients with diabetes, hypertension, or kidney disease to assess kidney function and detect early signs of kidney damage. The test should be done at the following times:

• At diagnosis of diabetes or hypertension
• Annually in patients with diabetes or hypertension 2
• When there is a change in kidney function or medication that may affect kidney function
• In patients with a history of kidney disease or kidney damage. The ACR result is calculated by dividing the urine albumin concentration by the urine creatinine concentration, and the result is expressed in milligrams per gram (mg/g) or milligrams per millimole (mg/mmol). An ACR result of 30 mg/g or higher indicates kidney damage and requires further evaluation and monitoring 3, 4.

Important Considerations

• The first morning void is the preferred sample for ACR measurement 1, 4
• If the first morning void is not possible, the test should be done at the same time of day to minimize variability 1
• The patient should be well hydrated and should not have ingested food within the preceding 2 hours or have exercised before the test 1
• Semiquantitative uACR dipsticks can be used to detect early kidney disease and assess cardiovascular risk when quantitative tests are not available 1
• Confirmatory tests should be ordered if the initial test results are positive or if there are any factors that may affect the interpretation of the measurements 4

Frequency of Measurement

• Annual measurement of uACR is recommended for adults with diabetes 2
• Every 6 months measurement of uACR is recommended if the eGFR is <60 mL/min/1.73 m2 and/or albuminuria is >30 mg/g creatinine in a spot urine sample 2, 3

From the Research

Measuring Creatinine (Creat)/Albumin Ratio

• The Creatinine (Creat)/Albumin ratio, also known as the albumin-to-creatinine ratio (ACR), is a diagnostic component of chronic kidney disease (CKD) 1.
• The ACR can be measured in a random urine sample, but studies have shown that first morning voids are more reliable than spot urine samples to assess microalbuminuria 2.
• Measuring ACR in a first morning void can provide a more accurate estimate of 24-hour urinary albumin excretion, with a lower prevalence of microalbuminuria compared to spot urine samples 2.

Timing of Measurement

• The best time to measure the ACR is in the first morning void, as it has been shown to be more reliable than spot urine samples 2.
• A study found that the ACR measured in a first morning void correlated well with 24-hour urinary albumin excretion, with a similar prevalence of microalbuminuria 2.
• Another study found that the use of confirmed increased ACR, defined as the presence of ACR ≥30 mg/g in both samples taken within 10 days, resulted in a lower overall prevalence of CKD compared to first morning urine or random spot urine only 1.

Alternative Methods

• Random urine protein-to-creatinine (PCR) and albumin-to-creatinine (ACR) ratios have been proposed as alternatives to 24-hour urine measurements, and have been shown to accurately predict 24-hour protein and albumin loss in patients with kidney disease 3.
• Point-of-care testing devices, such as the CLINITEK Microalbumin and DCA 2000+, can be used to measure ACR and rule out increased urinary albumin excretion in patients with kidney disease 4.